1. Field of the Invention
The present invention relates to systems and methods for computerized monitoring the levels of consciousness of patients admitted to medical units such as intensive care units, emergency rooms, operating rooms, etc. Specifically it automates and ultimately completely eliminates the need for human assessment of the most commonly used coma scorexe2x80x94the Glasgow Coma Score (GCS), while still using the same scale.
2. Description of the Prior Art
The Glasgow Coma Scale (GCS) was proposed by Teasdale and Jennett (Teasdale and Jennett 1974) and further elaborated Avezaat et. al., xe2x80x9cA Scoring Device For The Level Of Consciousness: The Glasgow xe2x80x9cComaxe2x80x9d Scalexe2x80x9d Ned Tijdschr Geneeskd 121 2117-21 (1977). GCS is the most widely used scoring system in quantifying level of consciousness following traumatic brain injury. It is used primarily because it is simple, has a relatively high degree of inter-observer reliability, and because it correlates well with outcome following severe brain injury.
GCS is comprised of three components: eye openingxe2x80x94E; motor responsexe2x80x94M; and verbal responsexe2x80x94V. (1) The eye opening is scored on a scale from 1 to 4. A score of 1 is assigned to a patient who is incapable of opening his or her eyes. In contrast, a 4 is assigned if the patient opens his or her eyes spontaneously. If a patient is unable to open his/her eyes spontaneously, but is capable of responding to verbal commands, such as xe2x80x9copen your eyesxe2x80x9d, a score of 3 is assigned. If eye opening cannot be elicited by a verbal command, but can be caused by applying a painful stimulus, the response is scored as 2.
(2) The motor response is scored on a scale from 1 to 6. A maximum score of 6 is assigned to a patient capable of obeying verbal commands such as xe2x80x9cShow me two fingersxe2x80x9d. If the patient does not react to verbal commands, but can localize painful stimuli by moving his or her arm toward the pain source in an attempt to remove the irritant, he or she will receive a score of 5. A patient only capable of a withdrawal response (a reflexive non-localizing movement) is assigned a score of 4. A score of 3 is given to an abnormal flexion response in which the arms are flexed at the elbows. If the motor response is an abnormal rigid extension (xe2x80x9cbrain stem levelxe2x80x9d) the score is 2. A minimum score of 1 is assigned to a patient who produces no motor response to verbal or pain stimulus.
(3) The verbal response is scored on a scale from 1 to 5. A maximal verbal score of 5 is given to a patient who is oriented and converses cohesively. A patient who can speak intelligibly, but is disoriented (i.e., unable to answer questions such as xe2x80x9cWho are you?xe2x80x9d or xe2x80x9cWhere are you?xe2x80x9d) is assigned a verbal score of 4. A score of 3 is given to a patient who utters inappropriate words in response to verbal questions. If the patient produces only incomprehensive sounds he or she will receive a score of 2. The absence of a verbal response is designated as 1 on the verbal scale. Often patients in the ICU are intubated; resulting in a mechanical obstruction of their airways which prevents them from speaking. In such cases a verbal score of 1 v is logged. The total maximal Glasgow Coma Score is 15 while the minimal score is 3. Table 1 is a summary of the Glasgow Coma Scale.
The following example demonstrates a GCS assessment performed on a comatose patient. Prior to the GCS assessment the patient is situated in a standard position (hands on either side of the chest). The nurse is unable to observe spontaneous eye movements and subsequently determines that the patient is unconscious. In an attempt to elicit a response the nurse gives verbal commands such as xe2x80x9cJack open your eyesxe2x80x9d. This is repeated few times, each time successively louder. The patient""s eyes remain closed, however, so she proceeds to forcefully pinch (i.e., painfully) the skin on his shoulders (above the deltoid muscle). The patient does not localize the pain (does not move hand toward the pain source), so the nurse pinches skin on the inner side of his biceps, which the patient localizes, or tickles the patient""s nose with a Q-tipxe2x80x94an irritant which is localized as well. This is the end of the GCS exam. The patient was scored as GCS 7-8v (E2; M4-5; V1v).
FIG. 1 shows a cartoon view of the standard GCS assessment procedure as performed by nurses in hospitals around the world. It shows the various eyes, motor, and verbal responses as observed during GCS assessment.
The GCS assessment is part of standard patient care and is commonly incorporated in most hospitals"" written Policies and Practices manual. Specifically, in a neurosurgery ICU the GCS of every patient is assessed and manually recorded in the patient""s chart every hour or entered in a computer. Routinely, an attending nurse performs the procedure; however, the attending physician can also assess the GCS during his or her rounds. Normally it takes about two to five minutes to get the GCS depending on the patient""s state of consciousness. Besides neurosurgery ICUs, where the patients are usually in a somewhat impaired state of consciousness or comatose, the assessment of GCS is recommended every 4 hours in all non-neurological ICUs and a minimum of once a shift for patients on the hospital floor. GCS is also commonly used in the emergency room.
There are several reasons why it is desirable to have an automated method for measuring the GCS:
1) Availability of qualified human assessors: Unpredictable changes of the patient""s level of consciousness can occur any time, day and night, and critical care personnel might not always be at hand to capture such changes. An AGCS system can be programmed to assess the GCS automatically and repetitively as frequently as necessary.
2) Subjectivity and frequency of assessment: Since the assessment of GCS requires human intervention (clinical procedure by nurses or doctors), it is often subjective, and can not be always performed on a regular basis.
3) Variability and accuracy: The accuracy of the Glasgow Coma Score is critical. Despite its demonstrated reproducibility in published works, in actual practice there is substantial variability in performing, scoring and recording the GCS by bedside nurses (these are the health care workers who most frequently perform this test as a routine evaluation). It is not at all uncommon to see an abrupt change in the recorded GCS when there is xe2x80x9cchange of shiftxe2x80x9d, when a new nurse comes on duty: xe2x80x9cScoring is often performed incorrectly (e.g. nurses commonly and inappropriately score patients according to worst responsexe2x80x9d and therefore it is often inaccurate.
4) Reliability and reproducibility of the GCS in actual practice is important for physician monitoring of patient status. Decisions regarding non-invasive or invasive diagnostic testing or therapeutic management are often made based on changes in GCS. For instance, a significant (e.g., 2 point) decrease in GCS often will lead to the performance of a cranial CT scan, or an invasive cerebral angiogram, which may further result in a change in the patient""s treatment. If the GCS has been scored inaccurately, the patient will have been exposed to a potentially risky and unnecessarily costly procedure, or conversely, a change in mental state with implications for early intervention may be missed. The AGCS system will reliably and reproducibly provide the Glasgow coma score.
5) Inadequate personnel training for GCS assessment: Many patients with neurological problems, such as, stroke following coronary artery bypass surgery are managed in non-neurological/neurosurgical intensive care units. The nurses in these units do not have extensive training in neurological assessment and in the GCS. Neurological monitoring in such patients is therefore often sub-optimal and inaccurate. The GCS scoring is an important part of the initial assessment of patients sustaining acute brain injury from trauma. However, emergency department personnel often are not experienced at administering and scoring the GCS, and it often is recorded inaccurately. Furthermore, the multitude of activities which go on in the middle of an acute trauma resuscitation often make the performance, and particularly the repeated performance, of the GCS difficult.
Based on these reasons we believe that having an Automated Glasgow Coma scoring method and system available would be of great benefit in such situations. We further believe that such a system will be particularly attractive to the critical care community because the GCS is the most commonly and widely used scoring system today for quantifying the level of consciousness following traumatic brain injury (TBI).
Different coma scales have been proposed and used in a number of countries around the world. Some of the more notable are the Swedish Reaction Level Scale (RLS 85) Starmark et.al., xe2x80x9cThe Reaction Level Scale (Rls 85) Manual And Guidelinesxe2x80x9d Acta Neurochir 91 12-20 (1988), the Innsbruk Coma Scale (ICS) Benzer et.al., xe2x80x9cPrediction Of Non-Survival After Trauma: Innsbruck Coma Scalexe2x80x9d Lancet 338 977-8 (1991), the Munich Coma Scale (MCS) (Brinkmann et al 1976), the Canadian Neurological Scale Cote et.al. xe2x80x9cThe Canadian Neurological Scale: Validation And Reliability Assessmentxe2x80x9d Neurology 39 638-643 (1989), the Glasgow-Liege Scale (GLS), which is an attempt to improve upon the GCS, Born xe2x80x9cThe Glasgow-Liege Scale: Prognostic Value And Evolution Of Motor Response And Brain Stem Reflexes After Severe Head Injuryxe2x80x9d Acta Neurochirurgica 91 1-11 (1988), the Edinburg-2 coma scale Sugiura et.al., xe2x80x9cThe Edinburgh-2 Coma Scale: A New Scale For Assessing Impaired Consciousnessxe2x80x9d Neurosurgery 12 411-5 (1983), and others. The effectiveness of the Glasgow Coma Scale has been compared to several of these scales (e.g., Johnstone et.al. xe2x80x9cA Comparison Of The Glasgow Coma Scale And The Swedish Reaction Level Scalexe2x80x9d Brain Injury 7 501-506 (1993); (Sugiura et al 1983), Hall et.al. xe2x80x9cCharacteristics And Comparisons Of Functional Assessment Indices: Disability Rating Scale, Functional Independence Measure, And Functional Assessment Measurexe2x80x9d Journal of Head Trauma Rehabilitation 8 60-74 (1993). Alternatives to the GCS in the form of continuous performance tests have also been proposed, Wijdicks et.al., xe2x80x9cMeasurement Of Impaired Consciousness In The Neurological Intensive Care Unit: A New Testxe2x80x9d Journal of Neurology Neurosurgery and Psychiatry 64 117-119 (1998).
It should be emphasized that GCS is not used to substitute for the comprehensive neurological exam, but rather to screen for the necessity of performing it Segatore et.al. xe2x80x9cThe Glasgow Coma Scale: Time For Changexe2x80x9d Heart Lung 21 548-57 (1992) at pp. 556. Furthermore, there are several limitations of GCS, particularly in its middle range (Segatore and Way 1992). Unless it is administered by experienced professionals, it may lack reliability Morris, xe2x80x9cAssessment And Communication Of Conscious Level: An Audit Of Neurosurgical Referralsxe2x80x9d Injury 24 369-72 (1993), Rowley et.al. xe2x80x9cReliability And Accuracy Of The Glasgow Coma Scale With Experienced And Inexperienced Usersxe2x80x9d Lancet 337 535-8 (1991). It can be affected by a number of factors such as poisoning Chan et.al., xe2x80x9cThe Use Of Glasgow Coma Scale In Poisoningxe2x80x9d J Emerg Med 11 579-82 (1993) or paresis Proehl xe2x80x9cThe Glasgow Coma Scale: Do It And Do It Rightxe2x80x9d J Emerg Nurs 18 421-3 (1992). Nonetheless, while clearly not perfect, the GCS is widely used and indeed is the current standard of care in ICUs. Thus, its automation as proposed in this invention provides a useful adjunct in monitoring the status of comatose patients.
There are a number of technical developments in the fields of physiological monitoring both EMG and EOG, speech recognition/generation as well as in patient pain stimulation/modulation/control. The electromyogram, (EMG), refers to voltage potentials recorded from muscle(s), and the electrooculogram, (EOG), refers to voltage potentials recorded during eye movements. Many of these developments are described in the literature, and patents cover some. However, to our knowledge, presently there is no publication or patent, which has put together relevant prior art is such a fashion as to realize the AGCS method and device as presented below. There are only a few patents in the US Patent Office database which contain the keywords xe2x80x9cGlasgowxe2x80x9d and xe2x80x9cComaxe2x80x9d. GCS is mentioned in these patents only as a clinically relevant parameter monitored in the ICU. None of these patents, however, addresses even remotely the invention disclosed below.
There are numerous patents in the fields of signal processing and pattern matching and more specifically patents that relate to EEG, EMG and EOG. For instance Pardey, reported in Pardey et.al. xe2x80x9cPhysiological Monitoringxe2x80x9d, in US Patent Office (USA: USA) (1999) describes a system for monitoring insomnia or vigilance which employs a neural network to analyze electrical signals recorded from the patient and assign sleep or wakefulness stages and generate a hypnogram.
A method and device for evaluating an EEG carried out in the context of anesthesia and the intensive care unit was described by Schultz as reported in Schultz et.al. xe2x80x9cMethod And Device For Evaluating An EEG Carried Out In The Context Of Anaesthesia Or Intensive Carexe2x80x9d, U.S. Pat. No. 6,011,990 (2000). In this system, multivariate statistical methods are used to classify EEG patterns into clinically relevant behavioral states (e.g., waking, subvigilance, sleepiness, sleep, anesthesia, coma, etc.) of anaesthetized or critically ill patients. The system, however, does not produce a coma score.
Publications and patents in the field of voice recognition, and speech generation are also ubiquitous. In fact, there are also commercially available devices capable of accomplishing the voice generation/recognition tasks as they relate to the AGCS system. For instance, the Dragon software, or the IBM voice recognition package can be used as the voice recognition component of AGCS. Such technology is hereby incorporated by reference as prior art and we do not have any claims on it.
There are numerous papers, Tsen et.al. xe2x80x9cTranscutaneous Electrical Nerve Stimulation Does Not Augment Combined Spinal Epidural Labor Analgesia [In Process Citation]xe2x80x9d Can J Anaesth 47 38-42 (2000); Coates, xe2x80x9cTranscutaneous Electrical Nerve Stimulation: Tensxe2x80x94Practical Guidance On Applicationxe2x80x9d Pract Midwife 1 12-4 (1998) and several devices on the market for pain stimulation, modulation and assessment of the patients"" sensitivity to pain. Transcutaneous Electrical Nerve Stimulators (TENS) and variations thereof, are manufactured and sold by companies. Thermal pain stimulators are available from Medoc, Ltd. (http://medoc-web.com/pain.html) and have been described in the literature ( Allen et.al. xe2x80x9cNoxious Cutaneous Thermal Stimuli Induce A Graded Release Of Endogenous Substance P In The Spinal Cord: Imaging Peptide Action In Vivoxe2x80x9d J Neurosci 17 5921-7 (1997); Willer et al xe2x80x9cEncoding Of Nociceptive Thermal Stimuli By Diffuse Noxious Inhibitory Controls In Humansxe2x80x9d J Neurophysiol 62 1028-38 (1989). Again, such devices are incorporated here by reference.
There is no similar method or device for assessment of the GCS on the market or in the literature at present. Furthermore, presently there is no system on the market, which combines behavioral and physiologic observations into a net assessment of the level of consciousness.
The present invention comprises a method and a system which are provided for automated computerized assessment of the Glasgow Coma Score (GCS). What is disclosed is a method and a computerized system that automatically and reliably maps stimulus-induced physiologic measurements to the GCS. This system is no harder to use, nor more invasive, than current monitoring for vital signs in the ICU and therefore can be adopted in clinical practice. The AGCS method and system disclosed collects physiological data such as EMG and EOG as well as speech data, which are digitized and stored on-line.
There are three integrated functions that are performed by the AGCS system: (1) patient stimulation; (2) data acquisition; and (3) data analysis. Computer-controlled verbal or pain stimulators provide patient stimulation. The acquired data is continuously analyzed on-line. Physiological and speech data are automatically interpreted and mapped online to the Glasgow Coma Scale. An algorithm, which implements a decision tree is modeled after the decision process used achieves this by human assessors. The tree is traversed in real time during the process of the AGCS estimation. The term real-time describes a system 10 with negligible latency between input and output.
The nodes of this decision tree are stimulus/response pairs (tests) and its branches implement the logic of the standard Glasgow Coma assessment procedure. The end-leafs of the tree correspond to the possible GCS outcomes (4 in the Eye response, 5 in the Verbal, and 6 in the Motor). In addition, if the algorithm can not come to a definite classification of the patient""s responses, it automatically requests an additional assessment or notifies the nurse.
More specifically the invention is an apparatus for automated assessment of a degree of conscious in a patient comprising a computer having a program stored therein to assess consciousness of the patient. At least one sensor is coupled to the computer for sensing a patient response. At least one stimulator is coupled to the computer to generate a stimulus applied to the patient.
The sensor comprises at least one electrode coupled to the computer for sensing a physical response or movement and/or a microphone coupled to the computer configured to sense an audio response from the patient. The stimulator comprises a speaker coupled to the computer for producing an audio signal and/or a pain stimulator coupled to the computer to generate a pain stimulus in the patient.
The electrode or electrode assembly comprises an EMG and/or EOG electrode and associated electronics such as an amplifier and an A-to-D converter. The program stored in the computer provides the computer with a capability to record movement of the patient as sensed by the at least one electrode in response to a verbal cue provided by the computer through the speaker.
The program stored in the computer provides the computer with speech recognition capability of the audio response from the patient from the microphone which has the capability to recognize normal conversation, coherent speech, and/or the capability to recognize words included in the audio response from the patient. The program stored in the computer provides the computer with a capability to record audio responses from the patient as sensed by the microphone in response to a verbal cue provided by the computer through the speaker.
The program stored in the computer provides the computer with a capability to record movement from the patient as sensed by the at least one electrode and to produce a verbal cue through the speaker in response to the recorded movement.
The program stored in the computer provides the computer with a capability to produce a verbal cue through the speaker to record movement or lack thereof from the patient as sensed by the at least one electrode, and in response to the recorded movement or lack thereof to generate the pain stimulus through the pain stimulator.
The computer performs cycles comprising stimulation of the patient, recordation of patient response, analysis of patient response and categorization of patient response in which the pain stimulator or speaker is selectively activated to provide a stimulus beginning in a subsequent cycle dependent on categorization of patient response in a prior cycle.
The invention is also defined as a method of automated assessment of a degree of consciousness in a patient using a computer comprising the steps of sensing a response from the patient. The response is recorded in or by the computer. The response is characterizable in nature. The characterizable nature of the response is analyzed in the computer to determine its nature. The nature of the response is categorized in the computer, preferably in accord with the conventional Glasgow Coma Scoring protocol. The computer produces or causes a stimulus to be produced dependent on the categorization of the response, such as a verbal cue or a pain stimulus.
The step of sensing a response from the patient comprises sensing an audio response by means of a microphone and/or sensing movement by at least one electrode. The movement is sensed by at least one electrode and comprises sensing eye movement of the patient and muscular movement of the patient.
When the response is an audio response from the patient it is analyzed to whether the audio response is a normal conversational response to a verbal cue, is a coherent response to a verbal cue, and/or is a recognizable word uttered by the patient in response to a verbal cue.
Where the response is a movement by the patient the response is analyzed to determine whether the movement is an eye opening or not in response to a stimulus, and whether the movement is a muscular or not in response to a stimulus. When the response is a muscular movement or not in response to a stimulus the analysis determines if it is in response to a pain stimulus and/or an appropriate movement or not to a verbal stimulus.
In the case of an appropriate movement in response to a pain stimulus the analysis determines by means of at least one body electrode if flexion is normal or rigid, and/or whether extension of a limb is normal.
The various advantages of the present invention will become apparent to one skilled in the art by reading the following specification and by reference to the following drawings wherein like elements are referenced by like numerals.